Agricultural crop production requires a bed of soil prepared for planting. A field's soil bed, in order to be ready for planting, must be configured with alternating planting rows and furrows. A planting row is a mound of soil into which a crop seed or sapling is introduced at a regular interval for maturation and eventual harvesting. The furrows adjacent to each planting row provides a channel through which water can flow. The furrow primarily serves as an irrigation channel to distribute water to the field for use by the crop, however the furrows can also channel water out of the field in the case of rains or flooding. This water drainage is vital to crops that will rot in water saturated soils.
A harrow is an implement that farmers use primarily to breakup and smooth crop growing soils. Farms of all types require implements for harrowing. The task of properly preparing the ground for planting begins with the tilling and leveling of fallow soil. Besides performing this task, the harrow is also used to kill weeds and cover newly sown seeds.
Many farmers add fertilizers, pesticides or herbicides to the soil simultaneously with harrowing. These fertilizers and chemical additives are applied at early crop growth to provide the best possible growth medium for the crop. Tractor pulled harrows and spray rigs, as separate implements, typically provide these soil preparation functions.
Modern tractors can pull increasingly large harrowing implements. This increase in size enables the farmer to enlarge the scale of their farming operations by expanding their ability to economically prepare and maintain crop growing soils. However, other factors reduce the efficiency of the modem farm. The available acreage of arable land is declining world-wide. Conversion of farmland to non-farming uses is a primary reason for this decline, however much of this arable soil, though may be once in prime condition, degrades over the years as farm chemicals, wind erosion, salt formation and nutrient depletion from over-farming, take their respective tolls.
Additionally, the lack of economical, dependable and clean water casts another cloud on the farm operation. Dwindling ground water resources, water allocation rights disputes, and water pollution results in an inability to farm on land that would otherwise be productive but for the lack or uncertainty of water availability from planting through harvest.
Government regulations, in an attempt to correct current problems, often only further hobble the farmer. Land use and growth management laws effectively lock up potential farm lands. Additionally, agricultural pesticides and herbicides are under increasing scrutiny, resulting in frequent bans and restrictions on their application. These limitations result in a steady reduction in the farmer's ability to economically control weeds and pests.
Additionally, the disfavor of farm chemicals by the government and the public has induced a resurgence of interest in organic farming methods. Methods that employ non-chemical means to achieve weed and pest control are urgently needed to makeup for the loss of chemicals once depended upon as mainstays of the modern farm.
When herbicides became readily available in the 1960's, many farmers began to use a "no-till" method for growing crops. In the no-till system, wastes from the preceding crop are left on the field as a covering called mulch. Farmers spray the mulch with a herbicide and apply fertilizer. Rain water washes the chemicals down through the mulch and into the soil. Often, no further soil preparation is necessary and the seed bed is ready for planting.
The no-till method improves on traditional tilling methods in several ways. The mulch helps prevent erosion and keep moisture in the soil. By eliminating plowing and harrowing, the method saves both labor and tractor fuel. However, the no-till method also has certain disadvantages. Some weeds are not killed by herbicides, and so weed control becomes a problem. Seeding can be delayed because the mulch keeps fields cooler and moister than is desirable at the start of the growing season. In addition, the heavy use of herbicides may cause environmental problems. In most locations environmental regulations severely limit the use of herbicides.
Today, many farmers still use the no-till method. As an attempt to reap many of the benefits of the no-till system, while additionally achieving the weed and planting control offered by tilling, farmers are adopting reduced tillage or conservation tillage methods. In these methods, deep plowing is replaced by a less invasive implement, such as a harrow. Plant wastes are also left on the surface as mulch, to help control erosion and hold in moisture.
The pressures of water conservation, farm chemical regulation, erosion control and rising labor costs force more farmers to adopt reduced tillage systems as an ideal balance between the herbicide based no-till system and conventional, tillage intensive farm methods. A harrow implement is therefore needed to specifically suit the needs of a reduced tillage farming operation.
Additionally, certain lands have excellent potential for farming, despite topographical irregularities or a small defect in soil quality that prohibits the economical tilling, planting or, harvesting of a crop. The existence of small knolls and gullies can impede the effective, mechanized tilling of prime soils. Typically, these areas are simply bypassed and as a result, unproductive. Currently, large scale grading with heavy machinery is the only way to prepare for crop production in these irregularly contoured areas. Employing heavy machinery to grade hilly soil is expensive and often results in the exposure of inferior soils, especially where the topsoil is thin. For larger farms a narrow harrow, though able to follow irregular contours, is inefficient. The smaller harrow requires many more passes to cover the same area as a larger, conventionally sized harrow. Therefore, a need exists for a wide harrow with the ability to follow irregular contours. A harrow having such an ability would significantly improve the potential range of topography that could be farmed efficiently.
Clay soils also present problems with their inherent clods and hard soil surfaces. Clays are difficult to breakup and convert into a proper seed bed with conventional fillers and harrows. Currently, some harrow designs offer the ability to modify the harrow to suit a range of soil types or harrowing depths, but these modifications are difficult to make in the field or ineffective due to the design of the harrow. There is a need for a harrow better able to prepare substandard soils and giving the farmer an ability to cultivate a wider range of soil types. A need also exists for an improved harrow with more than one specific operational mode.
Harrows are farm implements that when pulled behind a horse or tractor can rake smooth, till, furrow and apply sprays to a field in preparation for planting. Most modem harrows apply the same principles as their horse drawn predecessors but on a larger scale.
There are three main types of harrows; the disc harrow, the spring-tine harrow, and the spike-tooth harrow. The disc, or disk, harrow includes a set of sharp discs, mounted on a shaft. As the disc harrow is pulled forward, the discs revolve, thereby cutting the soil. If the soil is not hard, a disc harrow can be used as both harrow and plow. Disc harrows are the most successful harrow type and came into wide use when farmers began using tractors instead of draft animals. An inherent problem with disc harrows is that they require more pulling power than do the other types of harrows. Further, disc harrows typically cut more deeply and more thoroughly turn the soil as compared to other harrow types. Deeply turning the soil is not desirable in most situations because it dries out the soil by exposing moist underlying soil. This is a significant problem when water is scarce or irrigation expensive. A harrow is needed, therefore, that dependably tills on the large scale of a modern disc harrow, but without the problem of soil moisture loss.
Soil that has been completely turned over by discing often remains stuck together in large chunks. With rising labor and fuel costs, a farmer cannot afford to make multiple passes over large tracts of farmland to prepare for planting. A harrow is needed that is better suited for shallow and even tilling, and so able to level, weed and prepare soils for planting in a single pass.
The second type of harrow, a spring-tine harrow, consists of a strong framework with steel tines attached to lateral frame members. With their spring action, the tines tear into the soil when the harrow moves. Essentially, the tines on the frame "comb" the soil as the harrow is pulled. The spring-tined harrows are well suited for broken-up and rocky ground, because the tines give when they encounter a rock or hard clod of soil.
A limitation with spring-tined harrows is that they work best on generally flat and well-tilled farmland. Irregular contours result in spotty tillage because tines are unable to penetrate into the lower-lying soils. Adjacent tines riding on higher ground lift the entire harrow and prevent any tines from contacting the lower soils. Even if a contour riding spring-tine harrow was developed, another problem remains that the required spring of the tines prevent them from penetrating and aggressively tilling hardened soil surfaces. Therefore, a harrow is needed that follows ground surface contours while combing the soil and aggressively tilling hardened soil.
The third main type of harrow is a spike-toothed harrow. A spike-toothed harrow uses teeth instead of tines, for a more aggressive "bite" into hardened soils. This invention is an improved variation of a spike-toothed harrow. Historically, spike-toothed harrows have consisted of a steel frame with lateral supports. Steel teeth on the lateral supports functions to "comb" the soil as the harrow is pulled. This harrow also traditionally performed best when employed on well-cleared land, without irregular contours.
Improvements to the spike-tooth harrow have been attempted with limited success. For instance, the U.S. Pat. No. 1,382,977 to Holmes shows a harrow with teeth connected to a hinged frame. The frame's hinges are perpendicular to the direction of travel, giving it some ability to ride surface contours, but not to grade and flatten the irregular terrain. The Holmes harrow has another problem in that the entire frame sinks deeply into softer soils, rendering the harrow very difficult to pull. In harder soils, the Holmes harrow rides upon the surface without tilling or scraping. The Holmes harrow fails to exhibit the flexibility to operate under a variety of soil types and conditions. Additionally, changing the lengths of its harrow teeth is impossible. A harrow is needed which is continuously useful until the emergence of crops. Such a harrow is needed to have the ability to either deeply breakup soils prior to planting and after harvest, or shallowly breakup soils without damaging the delicate shoots of emerging seedlings, as required.
The U.S. Pat. No. 1,712,483 to Sutherland narrowly improves upon the Holmes patent by having the ability to employ shorter teeth for pre-emergence harrowing. The Sutherland harrow, as with the Holmes harrow, fails to force the grading and leveling of the soil while also tracking upon the general contours of the ground surface. Therefore, a need exists for a harrow with improved tracking over uneven surface contours.
Improvements have also been achieved in spring-tined harrows. The U.S. Pat. No. 5,251,704 to Bourgault et al. claims a combination spray rig and harrow, with tractor powered takeoff booms that include harrow frames. The independently suspended harrow frames each support an array of tines. As described in Bourgault et al., the harrow's tine arrays line up across the back of the implement in a single line, each array shown with forty spring action tines, all rigidly mounted in the harrow frame. The individual harrow frames are dragged by the booms, attached by cables and chains. As with prior harrows, the Bourgault et al. harrow also fails to actively grade and smooth irregular contours in the soil. The multiple harrow frames in Bourgault et al. simply ride along contours with the take off booms as backstops. After harrowing, the field has essentially the same irregular contours as before the harrowing. The Bourgault et al. harrow rides the contours without the ability to actively flatten and smooth the soil surface.
Even with its improved abilities, the Bourgault et al. harrow is still essentially a spring-tined harrow. Its tines fail to breakup clods and forcibly bite into hardened surfaces that are especially prevalent in poor and fallow ground. The Bourgault et al. harrow also fails to adequately address the need for a harrow to till up until the emergence of crop seedlings. It has an adjustable tine angle that the operator can make in the field, but this adjustment is arbitrary and depends on tine pressure, soil conditions and tine tension. If the operator fails to accurately gauge any of these factors, or if a surface irregularity is encountered, the emerging shoots will be irreparably damaged. A need therefore exists for a harrow capable of tilling hard packed soils and at variable depths to avoid pre-emergent seedlings.
The Bourgault et al. harrow also fails to provide a mechanism for preparing irrigation furrows and seed rows. Due to the need for seed rows to be free from large rocks and clods of soil, a need exists for a harrow with the ability to form irrigation furrows and clear larger clod and rock from the seed rows. Also, the Bourgault et al. harrow fails to level the ground it passes over and its tines do not till aggressively, especially when encountering clay and hard packed soils. This is a problem shared by all spring tine harrows. Another problem it shares with currently used harrowing implements is its inability to be effectively and easily customized in the field for a wider range of uses. Crops at different stages of growth often neighbor each other. A harrow is needed with the ability to be customized in the field to handle the individual field's requirements, including tilling depth and seed row separation distances.
The Bourgault et al. harrow further includes a farm chemical spray rig. The rig has spray nozzles attached to a leading boom member. However, the leading boom member is positioned just prior to the harrow portion of the implement. The spray from these nozzles contacts the ground before its breakup by the harrow tines. This arrangement is undesirable. Preferably, a soil application must be applied to broken and tilled soil, penetrating below the surface, so that moist soil can be contacted and immediately covered by additional soil. A need exists for a harrow that incorporates a spray rig into a harrow that applies the spray onto the soil as it is tilled, instead of immediately before or after the tilling process.